A perpetual bond is a bond with no maturity date. Perpetual bonds are not redeemable but pay a steady stream of interest forever. Some of the only notable perpetual bonds in existence are those that were issued by the British Treasury to pay off smaller issues used to finance the Napoleonic Wars (1814). Some in the U.S. believe it would be more efficient for the government to issue perpetual bonds, which may help it avoid the refinancing costs associated with bond issues that have maturity dates.
[edit] Also been suggested for issue in Japan in 2016:
https://www.bloomberg.com/news/articles/2016-07-14/bernanke-floated-japan-perpetual-bonds-idea-to-abe-adviser-honda
A perpetual bond is also known as a consol, perpetual or perp. [edited]
Read more: Perpetual Bond Definition | Investopedia
https://www.investopedia.com/terms/p/perpetualbond.asp
See also:
https://en.wikipedia.org/wiki/Perpetual_bond